That filter will block all address with 3 consecutive digits. That is not a good idea. For a more effective block only for some site use:

/gmx.net*\d{3}\.(jpg|gif)/

That only block in this site (gmx.net).

Im using that filter to block banner images based in numbers:

/\d{3}x\d{2,3}|\d{2}x\d{3}/

They block ???x??? and ???x?? and ??x??? (? = one number), like 200x120, 20x120 or 60x125. But they don't block ??x?? (that ones sometimes are buttons on pages)..

Cya_________________Sorry for my english... /\ Who does not know is as who does not see... | Each head its sentence.
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